Well, it was prototyped in standard ml first[1], wasn't it? - then ported/re-implemented (shoehorned ;) into plain js.
So some things that sml has, and made sense in sml, had to become part of the library/language/framework that is react?
Later came reasonml (a ocaml dialect) which is a lot closer to sml than js - and I think the state handling reflects that, like the readme for reasonml variant of redux:
https://github.com/reasonml-community/reductive/blob/master/...
"The code behind Reductive is incredibly simple. The first 40 lines include the entire re-implementation of redux. The next ~40 lines are a re-implementation of the react-redux library (without the higher-order component connect style implementation)."
In a sense, react has always been a design pattern - and a library to support/enable that pattern in Javascript.
[1] https://www.reactiflux.com/transcripts/jordan-walke#come-ide...